Class Spider

Entrance of a crawler.
A spider contains four modules: Downloader, Scheduler, PageProcessor and
Pipeline.
Every module is a field of Spider.
The modules are defined in interface.
You can customize a spider with various implementations of them.
Examples:

Use FileCacheQueueScheduler to store urls and cursor in files, so that a
Spider can resume the status when shutdown.
Spider.create(new SimplePageProcessor("http://my.oschina.net/",
"http://my.oschina.net/*blog/*"))
.scheduler(new FileCacheQueueScheduler("/data/temp/webmagic/cache/")).run();